Bug 1074777 - If Loop server crashes, when trying to signing-up, we should inform the user about this fault

See bug https://bugzilla.mozilla.org/show_bug.cgi?id=1074777 please.
Could you do a lazy construction here, please? Note that this will be triggered as soon as this file is loaded even if we don't want to show the offline screen. I would add an `init` function and call it on `show` if it has not already being called before.